1. Field of the Invention
The present invention relates to a hydraulic actuator control circuit for controlling the operation of a single hydraulic actuator by controlling a hydraulic circuit including the hydraulic actuator and a plurality of valve groups, each formed of a plurality of selector valves, in which the working fluid supplied through one of a plurality of selector valves of one of a plurality of valve groups, each of a plurality of selector valves and the working fluid supplied to another valve group are supplied together to the hydraulic actuator.
2. Description of the Conventional Art
A conventional hydraulic actuator control method increases the operating speed of a hydraulic actuator by controlling a hydraulic circuit so that the working fluid discharged from one of the hydraulic pumps is supplied to one of two individual valve groups of selector valves and the working fluid discharged from the other hydraulic pump to the other valve group of selector valves, and simultaneously controlling the selector valves of the two valve groups of selector valves to supply all the working fluid discharged from the two hydraulic pumps is supplied to the hydraulic actuator.
Another conventional hydraulic actuator control method increases the operating speed of a hydraulic actuator by simultaneously supplying the working fluid delivered from one of the selector valves of one of two valve groups and the working fluid delivered from one of the selector valves of the other valve group so that the working fluid is supplied at an increased rate to the hydraulic actuator to increase the operating speed of the hydraulic actuator.
FIG. 2 shows a hydraulic circuit employing a logic valve for increasing the operating speed of a hydraulic actuator for operating the arm of a hydraulic shovel excavator.
Referring to FIG. 2, a first hydraulic pump 2, a second hydraulic pump 3 and a pilot pump 4 are driven by an engine 1 to discharge working fluid sucked up from a tank 19 at appropriate pressures limited by relief valves. The first hydraulic pump 2 is connected by a line 5 to a valve group A comprising selector valves 8, 9, 10 and 11. The second hydraulic pump 3 is connected by a line 6 to a valve group B comprising selector valves 12, 13 and 14. The pilot pump 4 is connected by a line 7 to a control system including a pilot valve 16. Indicated at 17 is a hydraulic actuator for operating the arm. When the pilot valve 16 is operated to apply a signal pressure to the side E of the selector valve 11, and the pilot chambers of shutoff valves 15 and 25, the selector valve 11 is shifted to the side E, the shutoff valve 25 connects the chamber of a logic valve 18 to the tank 19, and the shutoff valve 15 shuts-off the central bypass line 32 of the valve group B. Consequently, the working fluid supplied to the valve group A by the first hydraulic pump 2 flows through a line 20 into the head-side chamber of the hydraulic actuator and, at the same time, the working fluid supplied to the valve group B by second hydraulic pump 3 flows through the logic valve 18 and a line 22 and the line 20 into the head-side chamber of the hydraulic actuator 17 to actuate the hydraulic actuator 17.
When this hydraulic system including the above hydraulic circuit and the hydraulic actuator 17 is used for elaborately operating the arm b of a hydraulic shovel excavator as shown in FIG. 3 in finishing a side slope d or light digging work for leveling the fields or the ground, the control lever for operating the arm b must be elaborately operated to operate the arm b simultaneously with the actions of the boom a and the bucket c. Such a mode of control of the hydraulic circuit is difficult and requires skilled control.